1. Field of the Invention
The present invention is directed at verifying the authenticity of the source of an optical storage media device.
2. Description of the Related Art
Optical media is widely used for recording and storing digital data, such as software products, document data, and image data. Digital data such as software products and document data recorded on CD-ROMs are subject to unauthorized copying. There are numerous copy protection technologies and schemes in place to thwart counterfeiters. Technological developments which have made it easier for software manufacturers to provide inexpensive products in the marketplace have also made it easier for software pirates to cheaply replicate and profitably market large volumes of optical media such as CDs and DVDs.
There are many different types of software piracy. End-user piracy is the copying of software without appropriate licensing for each copy. Pre-installed software piracy is when an illicit computer manufacturer takes one copy of software and illegally installs it on more than one computer. Internet piracy is the downloading of unauthorized software over the Internet. Counterfeiting is the making and distribution of illegal copies of software in packaging that replicates a legitimate manufacturer's packaging. Counterfeit media range in quality from hand-labeled recordable CDs to high quality replicas of genuine installation CD's and DVD's.
To defeat counterfeit media, a number of techniques are used. One scheme requires product validation by the software manufacturer upon installation of the software of an end user machine. Communication must be made between an installed version of the software and the manufacturer site before the software will run effectively on the end computer. Another method involves software manufacturers creating a unique physical signature or watermark in the pit/land structure of optical media. Although this signature could be created for each disk, typically this type of signature is created for an entire version or “run” of software as pressed on media, due to the difficulties involved in the manufacturing process.
One such physical signature uses latency data encoded into the disk in a manner not generally detectable to the user. Normally, data is written to a conventional optical disc master so that the data may be subsequently recovered uniformly while the photoresist (photosensitive) coated glass master disc is rotated at a constant linear velocity. The fixed frequency T is selected to write an extended frequency modulation (EFM) signal on the disk and the rotational velocity of the disc is successively decreased as the writing assembly is moved from the inner diameter (ID) to the outer diameter (OD). The EFM signal is a high frequency two-state signal with pulse durations that correspond to the range of data symbols to be written to the disc. In this way, all of the pits and lands of a given symbol length have nominally the same physical size regardless of location on the disc. The data are subsequently retrieved at a substantially constant readback data rate (frequency) and the linear velocity of the disc is adjusted to maintain this data rate within a selected range.
In one example of a physical latency watermark, a digital signature is “baked” into the media by selectively changing the rate at which data appears on at least certain locations on the disc. Some of the data symbols of track are written by at a nominal data rate, while others are written by the at a different rate (in this case, a higher or lower rate), so each symbol of track is substantially shorter or longer in length as compared to the nominal lengths of the symbols of a nominal track. This increase or decrease in data rate can be readily accomplished by increasing the timing frequency F, or the rotational velocity, V of the disc during writing operation of the glass master. If this signature is provided on a master disk, these changes are subsequently transferred to all disks in the resulting production run through an electroplating process metal of transferring the digital bits from “father” to “mother” to “son” (a.k.a “stamper”). This process is also known in the trade as “generational metalwork”. The stamper is the entity that is mounted into the injected molding machine mold cavity and is the negative of the final playback image found on the resulting CD or DVD.
In some cases, the variation in latency can be subtle enough so that the change does not affect the reading device's ability to recover the data from the end-user disk. However, this information latency variation is not normally detectable to the end-user user in the normal course of the installation process. This specialized or custom information can be used by a read back system to determine the authenticity or “genuineness” of the disk.